Relationship between nasal colonization and ventilator-associated pneumonia and the role of the environment in transmission of Staphylococcus aureus in intensive care units

Prospective Nasal Screening for Methicillin-Resistant Staphylococcus aureus in Critically Ill Patients With Suspected Pneumonia

We carried out a prospective de-escalation study based on methicillin-resistant Staphylococcus aureus (MRSA) nasal cultures in intensive care unit patients with suspected pneumonia. Days of anti-MRSA therapy was significantly reduced in the intervention group (2 [0–3] days vs 1 [0–2] day; P < .01). Time to MRSA de-escalation was also shortened in the intervention group.

Nasal Microbiota and Infectious Complications After Elective Surgical Procedures

IMPORTANCE

The association of the nasal microbiome with outcomes in surgical patients is poorly understood.

OBJECTIVE

To characterize the composition of nasal microbiota in patients undergoing clean elective surgical procedures and to examine the association between characteristics of preoperative nasal microbiota and occurrence of postoperative infection.

DESIGN, SETTING, AND PARTICIPANTS

Using a nested matched case-control design, 53 individuals who developed postoperative infection were matched (approximately 3:1 by age, sex, and surgical procedure) with 144 individuals who were not infected (ie, the control group). The 2 groups were selected from a prospective cohort of patients undergoing surgical procedures at 2 tertiary care university hospitals in Baltimore, Maryland, who were at high risk for postoperative infectious complications. Included individuals were aged 40 years or older; had no history of autoimmune disease, immunocompromised state, immune-modulating medication, or active infection; and were scheduled to undergo elective cardiac, vascular, spinal, or intracranial surgical procedure. Data were analyzed from October 2015 through September 2020.

EXPOSURES

Nasal microbiome cluster class served as the main exposure. An unsupervised clustering method (ie, grades of membership modeling) was used to classify nasal microbial samples into 2 groups based on features derived from 16S ribosomal RNA gene sequencing. The microbiome cluster groups were derived independently and agnostic of baseline clinical characteristics and infection status.

MAIN OUTCOMES AND MEASURES

Composite of surgical site infection, bacteremia, and pneumonia occurring within 6 months after surgical procedure.

RESULTS

Among 197 participants (mean [SD] age, 64.1 [10.6] years; 63 [37.7%] women), 553 bacterial taxa were identified from preoperative nasal swab samples. A 2-cluster model (with 167 patients in cluster 1 and 30 patients in cluster 2) accounted for the largest proportion of variance in microbial profiles using grades of membership modeling and was most parsimonious. After adjusting for potential confounders, the probability of assignment to cluster 2 was associated with 6-fold higher odds of infection after surgical procedure (odds ratio [OR], 6.18; 95% CI, 3.33-11.7; P < .001) independent of baseline clinical characteristics, including nasal carriage of Staphylococcus aureus. Intrasample (ie, α) diversity was inversely associated with infectious outcome in both clusters (OR, 0.57; 95% CI, 0.42-0.75; P < .001); however, probability of assignment to cluster 2 was associated with higher odds of infection independent of α diversity (OR, 4.61; 95% CI, 2.78-7.86; P < .001).

CONCLUSIONS AND RELEVANCE

These findings suggest that the nasal microbiome was an independent risk factor associated with infectious outcomes among individuals who underwent elective surgical procedures and may serve as a biomarker associated with infection susceptibility in this population.

The History of Methicillin-Resistant Staphylococcus aureus in Brazil

Since the emergence of MRSA in the 1960s, a gradual increase in infections by resistant bacteria has been observed. Clinical manifestations may vary from brand to critical condition due to host risk factors, as well as pathogen virulence and resistance. The high adaptability and pathogenic profile of MRSA clones contributed to its spread in hospital and community settings. In Brazil, the first MRSA isolates were reported in the late 1980s, and since then different genetic profiles, such as the Brazilian epidemic clone (BEC) and other clones considered a pandemic, became endemic in the Brazilian population. Additionally, Brazil's MRSA clones were shown to be able to transfer genes involved in multidrug resistance and enhanced pathogenic properties. These events contributed to the rise of highly resistant and pathogenic MRSA. In this review, we present the main events which compose the history of MRSA in Brazil, including numbers and locations of isolation, as well as types of staphylococcal cassette chromosome mec (SCCmec) found in the Brazilian territory.

Evasion of host defenses by intracellular Staphylococcus aureus

Staphylococcus aureus is one of the leading causes of hospital and community-acquired infections worldwide. The increasing occurrence of antibiotic resistant strains and the high rates of recurrent staphylococcal infections have placed several treatment challenges on healthcare systems. In recent years, it has become evident that S. aureus is a facultative intracellular pathogen, able to invade and survive in a range of cell types. The ability to survive intracellularly provides this pathogen with yet another way to evade antibiotics and immune responses during infection. Intracellular S. aureus have been strongly linked to several recurrent infections, including severe bone infections and septicemias. S. aureus is armed with an array of virulence factors as well as an intricate network of regulators that enable it to survive, replicate and escape from a number of immune and nonimmune host cells. It is able to successfully manipulate host cell pathways and use it as a niche to multiply, disseminate, as well as persist during an infection. This bacterium is also known to adapt to the intracellular environment by forming small colony variants, which are metabolically inactive. In this review we will discuss the clinical evidence, the molecular pathways involved in S. aureus intracellular persistence, and new treatment strategies for targeting intracellular S. aureus.

The Clinical Utility of Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Screening to Rule Out MRSA Pneumonia: A Diagnostic Meta-analysis With Antimicrobial Stewardship Implications

Background

Recent literature has highlighted methicillin-resistant Staphylococcus aureus (MRSA) nasal screening as a possible antimicrobial stewardship program tool for avoiding unnecessary empiric MRSA therapy for pneumonia, yet current guidelines recommend MRSA therapy based on risk factors. The objective of this meta-analysis was to evaluate the diagnostic value of MRSA nasal screening in MRSA pneumonia.

Methods

PubMed and EMBASE were searched from inception to November 2016 for English studies evaluating MRSA nasal screening and development of MRSA pneumonia. Data analysis was performed using a bivariate random-effects model to estimate pooled sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

Results

Twenty-two studies, comprising 5163 patients, met our inclusion criteria. The pooled sensitivity and specificity of MRSA nares screen for all MRSA pneumonia types were 70.9% and 90.3%, respectively. With a 10% prevalence of potential MRSA pneumonia, the calculated PPV was 44.8%, and the NPV was 96.5%. The pooled sensitivity and specificity for MRSA community-acquired pneumonia (CAP) and healthcare-associated pneumonia (HCAP) were 85% and 92.1%, respectively. For CAP and HCAP both the PPV and NPV increased, to 56.8% and 98.1%, respectively. In comparison, for MRSA ventilated-associated pneumonia, the sensitivity, specificity, PPV, and NPV were 40.3%, 93.7%, 35.7%, and 94.8%, respectively.

Conclusion

Nares screening for MRSA had a high specificity and NPV for ruling out MRSA pneumonia, particularly in cases of CAP/HCAP. Based on the NPV, MRSA nares screening is a valuable tool for AMS to streamline empiric antibiotic therapy, especially among patients with pneumonia who are not colonized with MRSA.

Systematic Review of the Clinical Utility of Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Screening for MRSA Pneumonia

Objective: To describe the diagnostic performance characteristics of methicillin-resistant Staphylococcus aureus (MRSA) nasal screening for patients with pneumonia. Data Sources: PubMed and Scopus were searched from 1 January 1990 to 12 December 2018 using terms methicillin-resistant Staphylococcus aureus AND (screening OR active surveillance OR surveillance culture OR targeted surveillance OR chromogenic OR PCR OR polymerase chain reaction OR rapid test) AND (nares OR nasal) AND (pneumonia OR respiratory). Study Selection and Data Extraction: Relevant studies in humans and English were considered. Data Synthesis: In all, 19 studies, including 21 790 patients, were included. Nasal screening for MRSA had a high negative predictive value (NPV; 76% to 99.4% for relevant studies) across all types of pneumonia. Time from nasal screening to culture varied across studies. Relevance to Patient Care and Clinical Practice: MRSA nasal screening has a high NPV for MRSA involvement in pneumonia. Utilizing this test for antimicrobial stewardship program (ASP) purposes can provide a valuable tool for reducing unwarranted anti-MRSA agents and may provide additional cost benefits. A cutoff of 7 days between nasal swab and culture or infection onset seems most appropriate for use of this test for anti-MRSA agent de-escalation for ASP purposes. Conclusions: Consideration for the inclusion of the utility of MRSA nasal screening in MRSA pneumonia should be made for future pneumonia and ASP guidelines. Additional studies are warranted to fully evaluate specific pneumonia classifications, culture types, culture timing, and clinical outcomes associated with the use of this test in patients with pneumonia.

Evaluating the Efficacy of Nanosil Mouthwash on the Preventing Pulmonary Infection in Intensive Care Unit: a Randomized Clinical Trial

Introduction

Oral and Oro-pharynx colonization and Micro-aspiration of discharges are two important processes in ventilator-associated pneumonia (VAP). So, this study design to investigated the preventive effect of oral decontamination program by Nanosil mouthwash on incidence of ventilator-associated pneumonia.

Methods

80 newly hospitalized patients who admitted in intensive care unit (ICU) of Amin Medical Education Center were enrolled to a randomized clinical trial study. Patients were randomly divided into two equal groups. In the intervention group, a multi-stage oral decontamination program was performed by using Nanosil mouthwash three times a day, and in the control group oral decontamination was performed by Chlorhexidine 0.12% with same method. The oral decontamination program was continuing for five days. The VAP was diagnosed with a version of modified clinical pulmonary infection scale (MCPIS) on the first and fifth days.

Results

In compare the case and control groups, there wasn't observed significant difference in age, gender, underling disease, smoking, and primary mean scores of MCPIS, sequential organ failure assessment (SOFA) and Glasgow coma scale (GCS) (P>0.05). In the both groups, the mean scores of SOFA and GCS were significantly improve in fifth day (P<0.05). After five days follow up, the mean score of MCPIS (1.2±0.1 vs. 3.5±0.3, P<0.001) and pneumonia rate (2.7% vs. 23.7%, P=0.008) were significantly lower in case group. But, the mortality rate was same in both groups (P>0.05).

Discussion

The use of oral care program with Nanosil mouthwash is better than Chlorhexidine for the prevention of VAP in patients who admitted in ICU.

Role of the Clinical Microbiology Laboratory in Antimicrobial Stewardship

For adequate antimicrobial stewardship, microbiology needs to move from the laboratory to become physically and verbally amenable to the caregivers of an institution. Herein, we describe the contributions of our microbiology department to the antimicrobial stewardship program of a large teaching hospital as 10 main points ranging from the selection of patients deemed likely to benefit from a fast track approach, to their clinical samples, or the rapid reporting of results via a microbiology hotline, to rapid searches for pathogens and susceptibility testing. These points should serve as guidelines for similar programs designed to decrease the unnecessary use of antimicrobials.

Risk factors for health care-associated infection in hospitalized adults: Systematic review and meta-analysis

BACKGROUND

Health care-associated infections (HAIs) are a public health problem that increase health care costs. This article aimed to systematically review the literature and meta-analyze studies investigating risk factors (RFs) independently associated with HAIs in hospitalized adults.

METHODS

Electronic databases (MEDLINE, Embase, and LILACS) were searched to identify studies from 2009-2016. Pooled risk ratios (RRs) or odds ratios (ORs) or mean differences (MDs) and 95% confidence intervals (CIs) were calculated and compared across the groups. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.

RESULTS

Of 867 studies, 65 met the criteria for review, and the data of 18 were summarized in the meta-analysis. The major RFs independently associated with HAIs were diabetes mellitus (RR, 1.76; 95% CI, 1.27-2.44), immunosuppression (RR, 1.24; 95% CI, 1.04-1.47), body temperature (MD, 0.62; 95% CI, 0.41-0.83), surgery time in minutes (MD, 34.53; 95% CI, 22.17-46.89), reoperation (RR, 7.94; 95% CI, 5.49-11.48), cephalosporin exposure (RR, 1.77; 95% CI, 1.30-2.42), days of exposure to central venous catheter (MD, 5.20; 95% CI, 4.91-5.48), intensive care unit (ICU) admission (RR, 3.76; 95% CI, 1.79-7.92), ICU stay in days (MD, 21.30; 95% CI, 19.81-22.79), and mechanical ventilation (OR, 12.95; 95% CI, 6.28-26.73).

CONCLUSIONS

Identifying RFs that contribute to develop HAIs may support the implementation of strategies for their prevention, therefore maximizing patient safety.

Respective impact of implementation of prevention strategies, colonization with multiresistant bacteria and antimicrobial use on the risk of early- and late-onset VAP: An analysis of the OUTCOMEREA network

Rationale

The impact of prevention strategies and risk factors for early-onset (EOP) versus late-onset (LOP) ventilator-associated pneumonia (VAP) are still debated.

Objectives

To evaluate, in a multicenter cohort, the risk factors for EOP and LOP, as the evolution of prevention strategies.

Methods

7,784 patients with mechanical ventilation (MV) for at least 48 hours were selected into the multicenter prospective OUTCOMEREA database (1997–2016). VAP occurring between the 3^rd and 6^th day of MV defined EOP, while those occurring after defined LOPs. We used a Fine and Gray subdistribution model to take the successful extubation into account as a competing event.

Measurements and main results

Overall, 1,234 included patients developed VAP (EOP: 445 (36%); LOP: 789 (64%)). Male gender was a risk factor for both EOP and LOP. Factors specifically associated with EOP were admission for respiratory distress, previous colonization with multidrug-resistant Pseudomonas aeruginosa, chest tube and enteral feeding within the first 2 days of MV. Antimicrobials administrated within the first 2 days of MV were all protective of EOP. ICU admission for COPD exacerbation or pneumonia were early risk factors for LOP, while imidazole and vancomycin use within the first 2 days of MV were protective factors. Late risk factors (between the 3^rd and the 6^th day of MV) were the intra-hospital transport, PAO2-FIO2<200 mmHg, vasopressor use, and known colonization with methicillin-resistant Staphylococcus aureus. Among the antimicrobials administered between the 3^rd and the 6^th day, fluoroquinolones were the solely protective one.Contrarily to LOP, the risk of EOP decreased across the study time periods, concomitantly with an increase in the compliance with bundle of prevention measures.

Conclusion

VAP risk factors are mostly different according to the pneumonia time of onset, which should lead to differentiated prevention strategies.

Prevalence and correlates of MRSA and MSSA nasal carriage at a Ugandan regional referral hospital

Background

Despite increasing antimicrobial resistance globally, data are lacking on prevalence and factors associated with Staphylococcus aureus (SA) and MRSA carriage in resource-limited settings.

Objectives

To determine the prevalence of SA and MRSA nasal carriage and factors associated with carriage among Ugandan regional referral hospital patients.

Methods

We enrolled a cross-section of 500 adults, sampling anterior nares for SA and MRSA carriage using Cepheid Xpert SA Nasal Complete.

Results

Mean age was 37 years; 321 (64%) were female and 166 (33%) were HIV infected. Overall, 316 (63%) reported risk factors for invasive SA infection; 368 (74%) reported current antibiotic use. SA was detected in 29% and MRSA in 2.8%. MRSA and MSSA carriers were less likely than SA non-carriers to be female (50% and 56% versus 68%, P  = 0.03) or to have recently used β-lactam antibiotics (43% and 65% versus 73%, P  = 0.01). MRSA carriers were more likely to have open wounds than MSSA carriers and SA non-carriers (71% versus 27% and 40%, P  = 0.001) and contact with pigs (21% versus 2% and 6%, P  = 0.008). MRSA carriage ranged from 0% of HIV clinic participants to 8% of inpatient surgical ward participants ( P  =   0.01). In multivariable logistic regression analysis, male sex was independently associated with SA carriage (OR 1.68, 95% CI 1.12-2.53, P  =   0.01) and recent β-lactam antibiotic use was associated with reduced odds of SA carriage (OR 0.61, 95% CI 0.38-0.97, P  =   0.04).

Conclusions

MRSA nasal carriage prevalence was low and associated with pig contact, open wounds and surgical ward admission, but not with HIV infection.

Effects of Coal Fly Ash Particulate Matter on the Antimicrobial Activity of Airway Surface Liquid

BACKGROUND

Sustained exposure to ambient particulate matter (PM) is a global cause of mortality. Coal fly ash (CFA) is a byproduct of coal combustion and is a source of anthropogenic PM with worldwide health relevance. The airway epithelia are lined with fluid called airway surface liquid (ASL), which contains antimicrobial proteins and peptides (AMPs). Cationic AMPs bind negatively charged bacteria to exert their antimicrobial activity. PM arriving in the airways could potentially interact with AMPs in the ASL to affect their antimicrobial activity.

OBJECTIVES

We hypothesized that PM can interact with ASL AMPs to impair their antimicrobial activity.

METHODS

We exposed pig and human airway explants, pig and human ASL, and the human cationic AMPs β-defensin-3, LL-37, and lysozyme to CFA or control. Thereafter, we assessed the antimicrobial activity of exposed airway samples using both bioluminescence and standard colony-forming unit assays. We investigated PM-AMP electrostatic interaction by attenuated total reflection Fourier-transform infrared spectroscopy and measuring the zeta potential. We also studied the adsorption of AMPs on PM.

RESULTS

We found increased bacterial survival in CFA-exposed airway explants, ASL, and AMPs. In addition, we report that PM with a negative surface charge can adsorb cationic AMPs and form negative particle-protein complexes.

CONCLUSION

We propose that when CFA arrives at the airway, it rapidly adsorbs AMPs and creates negative complexes, thereby decreasing the functional amount of AMPs capable of killing pathogens. These results provide a novel translational insight into an early mechanism for how ambient PM increases the susceptibility of the airways to bacterial infection. https://doi.org/10.1289/EHP876.

Preventing Ventilator-Associated Infections

Mechanical ventilator use is fraught with risk of complications. Ventilator-associated pneumonia (VAP) is a common complication that prolongs stays on the ventilator and increases mortality and costs. The Centers for Disease Control and Prevention recommend the use of the term, ventilator-associated event. Prevention and/or interruption of cycle of inflammation, colonization of respiratory tract, and ventilator-associated tracheobronchitis are key to managing VAP. Modifying risk factors using a ventilator bundle is considered standard of care. The contentious factors and the lack of support for early tracheotomy, parenteral nutrition, and monitoring of gastric residuals are also addressed. Finally, the role of ventilator-associated tracheobronchitis in VAP is discussed.

Human Infections with Staphylococcus aureus CC398

Staphylococcus aureus isolates belonging to clonal cluster 398 (CC398) have emerged over the previous decade as a risk to livestock workers. Though most of the research to date has focused on colonization with these strains, a number of infections have also been documented, ranging from mild skin infections to more serious invasive infections and even death. Here, we review existing reports of human infections with CC398 and discuss their geographic distribution, general characteristics, and implications for future research. We identified 74 publications describing CC398 infections in humans in 19 different countries, suggesting this is an emerging worldwide issue.

Heterogeneity in ess transcriptional organization and variable contribution of the Ess/Type VII protein secretion system to virulence across closely related Staphylocccus aureus strains

The Type VII protein secretion system, found in Gram-positive bacteria, secretes small proteins, containing a conserved W-x-G amino acid sequence motif, to the growth medium. Staphylococcus aureus has a conserved Type VII secretion system, termed Ess, which is dispensable for laboratory growth but required for virulence. In this study we show that there are unexpected differences in the organization of the ess gene cluster between closely related strains of S. aureus. We further show that in laboratory growth medium different strains of S. aureus secrete the EsxA and EsxC substrate proteins at different growth points, and that the Ess system in strain Newman is inactive under these conditions. Systematic deletion analysis in S. aureus RN6390 is consistent with the EsaA, EsaB, EssA, EssB, EssC and EsxA proteins comprising core components of the secretion machinery in this strain. Finally we demonstrate that the Ess secretion machinery of two S. aureus strains, RN6390 and COL, is important for nasal colonization and virulence in the murine lung pneumonia model. Surprisingly, however, the secretion system plays no role in the virulence of strain SA113 under the same conditions.